Physics

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Showing 251 to 275 of 1648 questions (page 11 of 66).

251. Above the Curie temperature, a ferromagnetic material becomes

A. diamagnetic B. paramagnetic C. superconducting D. more strongly ferromagnetic E. non-magnetic in the sense of losing all response

252. Stress within the elastic limit is

A. independent of strain B. directly proportional to strain C. inversely proportional to strain D. proportional to the square of strain E. zero

253. A p-n junction diode conducts appreciably when

A. reverse biased B. forward biased C. unbiased D. at absolute zero E. the depletion region widens

254. The output ripple frequency of a full wave rectifier fed from a 50 Hz supply is

A. 25 Hz B. 50 Hz C. 100 Hz D. 150 Hz E. zero

255. A Zener diode in a voltage regulator circuit is operated in

A. forward bias B. reverse bias beyond the breakdown voltage C. zero bias D. the saturation region E. the cut off region

256. Which logic gate is called a universal gate?

A. AND B. OR C. NOT D. NAND E. XOR

257. In an ideal operational amplifier, the input impedance and open loop gain are respectively

A. zero and zero B. infinite and infinite C. infinite and zero D. zero and infinite E. finite and unity

258. For a transistor operating as an amplifier, the emitter base junction and collector base junction are

A. both forward biased B. both reverse biased C. forward and reverse biased respectively D. reverse and forward biased respectively E. unbiased

259. Doping silicon with a pentavalent impurity produces

A. a p-type semiconductor B. an n-type semiconductor C. an insulator D. an intrinsic semiconductor E. a superconductor

260. According to the special theory of relativity, the speed of light in free space is

A. different for different observers B. the same for all inertial observers C. dependent on the source velocity D. dependent on the observer velocity E. infinite

261. In the photoelectric effect, the maximum kinetic energy of the emitted electrons is

A. hf B. hf + work function C. hf - work function D. work function - hf E. independent of frequency

262. The de Broglie wavelength of a particle of momentum p is

A. hp B. h/p C. p/h D. h/p2 E. h p2

263. The Compton effect demonstrates the

A. wave nature of light B. particle nature of light C. transverse nature of light D. polarization of X-rays E. interference of X-rays

264. Heisenberg's uncertainty principle states that the product of the uncertainties in position and momentum is

A. zero B. at least of the order of h/(4 pi) C. at most h D. equal to hf E. independent of h

265. The stopping potential in a photoelectric experiment depends on

A. the intensity of light only B. the frequency of light and the material C. the area of the cathode D. the distance of the source E. the polarization of light

266. According to Bohr's theory, the angular momentum of an electron in the nth orbit is

A. nh B. nh/(2 pi) C. h/(2 pi n) D. n2 h E. h/n

267. The spectral series of hydrogen that lies in the visible region is the

A. Lyman series B. Balmer series C. Paschen series D. Brackett series E. Pfund series

268. The ionization energy of a hydrogen atom in its ground state is

A. 3.4 eV B. 10.2 eV C. 13.6 eV D. 1.51 eV E. 27.2 eV

269. Laser action requires

A. thermal equilibrium B. population inversion C. a very low pumping rate D. incoherent sources E. a single energy level

270. The continuous part of an X-ray spectrum is produced by

A. electron transitions between inner shells B. deceleration of fast electrons in the target C. nuclear decay D. thermal emission from the filament E. stimulated emission

271. The radius of the nth Bohr orbit in hydrogen is proportional to

A. n B. n2 C. 1/n D. 1/n2 E. n3

272. Isotopes of an element have the same

A. mass number B. number of neutrons C. atomic number D. atomic mass E. binding energy

273. A radioactive sample has a half life of 10 days. The fraction remaining after 30 days is

A. 1/2 B. 1/4 C. 1/8 D. 1/16 E. 1/3

274. In beta minus decay, the atomic number of the nucleus

A. decreases by 1 B. increases by 1 C. decreases by 2 D. remains unchanged E. increases by 2

275. The energy released in nuclear reactions arises from

A. chemical bonding B. mass defect C. electron transitions D. frictional heating E. ionization

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